1. Field of the Invention
The present invention relates to a planter height and marker control system for use with an agricultural planter assembly which is adapted to be mechanically and hydraulically coupled to a tractor and which includes a frame, a plurality of planter units mounted to the frame, and two pairs of wheels assemblies mounted to the frame, one pair on each side of the center line of the planter assembly. More specifically, the present invention relates to an electrical-hydraulic control circuit of the system for parallel coupling the piston and cylinder mechanisms and for limiting the retraction of each piston rod of each piston and cylinder mechanism to a predetermined limit less than the full return stroke thereof on the lowering of the planter units, thereby to control the height of the planter frame above the ground and to provide limited movement of the wheel assemblies so that when one wheel assembly encounters an obstacle, it can move upwardly while the other wheel assembly moves downwardly as the planter assembly traverses uneven ground.
2. Description of the Prior Art
Heretofore, it has been proposed to provide a planter assembly having a planter frame, a plurality of planter units, e.g., eight equally spaced planter units, mounted to the frame, and at least two pairs of wheel assemblies on either side of the center line of the planter assembly and mounted to the frame. In such a previously proposed planter assembly, each wheel assembly has a double acting piston and cylinder mechanism associated therewith for pivoting the wheel assembly downwardly to raise the planters and to pivot the wheel assembly upwardly to lower the planters. The hydraulic circuit for operating the piston and cylinder mechanisms included a main valve assembly having at least three positions, the first position being a neutral position where coupling of the piston and cylinder mechanisms to a line from a pump and a line leading to a sump are blocked, a second position where the line from the pump is coupled to the head side of the cylinder of each piston and cylinder mechanism for causing extension of the piston rods and the line to the sump is connected to the piston rod side of each cylinder, and a third position where the line from the pump is coupled to the piston rod sides of the cylinders and the line to the sump is connected to the head sides of the cylinders in each piston and cylinder mechanism.
In the operation of the hydraulic circuit and main valve assembly, the main valve asembly is moved to the second position thereof to fully extend the piston rods to fully raise the planter units and is moved to the third position thereof to fully retract the piston rods to fully raise the wheel assemblies. With this arrangement, when the wheel assemblies are fully raised to fully lower the planter units, jarring of the planter assembly occurs when the wheels travel over uneven terrain. This has often resulted in awkward and uncomfortable operation of the planter assembly and has caused excessive stress and wear on the component parts of the planter assembly and the hydraulic system therefor.
Also, in the operation of a planter assembly, it is desired to raise and lower respective markers on opposite sides of the planter assembly each time the planter units of the assembly are raised and the tractor pulling the planter assembly turns the planter assembly 180.degree. to start another planting sweep. When this is done, it is desirable to provide means for planting the next group of adjacent rows in proper spaced relationship to the group of rows just planted. This is accomplished by dragging a marker along on the first planting sweep and then on the return planting sweep, aligning a wheel of the tractor with the track on the ground made by the marker which ensures proper spacing of the next group of rows being planted relative to the group of rows just planted. Heretofore, the operator in the cabin of the tractor would operate a hydraulic valve assembly for causing extension of a desired marker after the tractor has turned 180.degree. and retraction of the other marker.
At times, the operator will forget to extend the desired marker and it is desirable to provide means for automatically extending a desired marker and retracting the other marker after the planter units are raised and the tractor proceeds to turn 180.degree. to begin a return planting sweep across a section of ground.
As will be described in greater detail hereinafter, the planter height and marker control system of the present invention includes electrical-hydraulic control circuits for limiting the extent of retraction of the piston rods for the pair of parallel coupled piston and cylinder mechanisms for the pair of wheel assemblies on each side of the center line of the planter assembly so that relative movement of the piston rods can take place, whereby when uneven terrain is encountered, one wheel assembly can go up while the other wheel assembly goes down, in either one or both pairs of piston and cylinder mechanisms associated with a respective pair of wheel assemblies.
Also as will be described in greater detail hereinafter, the electrical-hydraulic control circuits include an automatic alternating marker system for causing automatic extension of a desired marker when the planter units are raised and retraction of the other marker.